1. Field of the Invention
The present invention relates generally to the field of water and wastewater treatment systems, and more particularly to systems utilizing an electrochemical cell to facilitate flocculation of particles in the water or wastewater to permit the discharge of treated wastewater to the environment or purification of potable water.
2. Description of Related Art
Contamination occurring in aqueous-based solutions has become a serious concern to society. In particular, problems associated with the disposal of industrial wastewater have been mounting. Disposing of the wastewater is not only very expensive and time consuming, but also extremely harmful to the environment. Some areas of concern in the disposal of wastewater, which are particularly suited to treatment using the subject system, are:
removal of emulsified oils, both petroleum hydrocarbons and food base oils;
partially dissolved contaminants which add to turbidity and color of water;
negatively charged metals such as arsenic, molybdenum, and chromium;
positively charged heavy metals such as copper, cadmium, nickel, lead, and zinc;
contaminants such as ammonia, mercury, arsenic and iron which react with oxygen;
contaminants which react with aluminum or iron such as chlorinated organics; and
poorly settling TSS (total suspended solids) such as silt, ink, wood extractives, clay and microorganisms.
One example of a particular contaminant of concern is petroleum hydrocarbon contaminants in shipyard wastewater, including the oily wastewater resulting from cleaning out ship bilges and fuel tanks. The primary concern with this wastewater is finding an effective method for its disposal. While various methods have been developed to deal with this oily waste, none have been entirely successful given the extremely varied nature and content of the contaminants in the water, with oil content ranging anywhere from 0.5% to 50% in volume. Included among the methods attempting to control these waste streams are a wide variety of chemical and physical procedures.
Chemical procedures have attempted to cause a predetermined reaction between chemical additives and impurities contained within the waste stream. The most common reactions are designed to cause the impurities and the chemical additives to coagulate, wherein the particles increase in size and then separate by either floating on or settling below the treated water. The most popular chemical utilized is alum, which when added to the wastewater, separates much of the waste out of the water. There are several problems with chemical coagulation in general, including the generation of very large quantities of residuals that need to be disposed of and imprecision because the amount of chemical necessary for a given volume must always be estimated due to the varying nature of the waste streams.
Physical procedures are designed to achieve similar results as chemical additive procedures, but to a lesser degree of purity in the final aqueous solution. Filters, centrifuges, plate separators, and clarifiers are the most common physical procedures employed to remove contaminants from aqueous solutions. In most cases, the impurities that are removed physically are suspended solids or poorly emulsified contaminants.
While the chemical and physical procedures of treating waste streams were thought to be adequate at one time, the results of disposal of solutions treated in this manner have been disastrous. Oceans, streams, lakes and underground wells have all fallen victim to the contamination resulting from the impurities that were not removed by these methods. In fact, because of the dumping of contaminated solutions, many rivers and streams are considered waste sites and entire lakes have been drained so that the lakebeds can be hauled away to be treated as hazardous waste. The main problem is that regardless of whether chemical procedures, physical procedures, or a combination of the two are utilized, the content of impurities in the wastewater remains in an unacceptable range.
While it was known that the purification of waste streams, and in particular the coagulation of contaminants without the addition of chemicals, could be accomplished through electrolytic treatment in a process called electrocoagulation, the wide range of contaminants, varying contaminant concentrations and large and variable volumes of wastewater in the industrial waste streams generally discouraged its use. However, patents directed to electrolytic treatment apparatuses, methods and systems can be found dating back to the early part of this century. Electrocoagulation is the process of de-stabilizing suspended, emulsified or dissolved contaminants in an aqueous medium by introducing an electrical current into the medium. Electrocoagulation generally takes place inside a substantially sealed treatment chamber, where the impurities are coagulated out of the aqueous medium.
Many other systems and cells have been disclosed and patented, each trying to convert contaminated water to purified water by separating the contaminants from the water. Unfortunately, none of these systems have been able to solve the problems of variability, number and concentration of contaminants associated with the treatment of industrial wastewater. These previous systems created large quantities of metal sludge and other contaminant sludge that added to the cost of disposal. Even systems that were able to overcome these problems had other problems such as high labor cost (batch and dump methods); large areas necessary for increased residence time, and high capital costs due to electrical power and maintenance (on-line electrical systems); and low efficiency (dilution with non-conductive materials). Other systems suffered from design problems such as not accounting for the production of generated gases or the build up of impurities onto the working electrodes, or creating an electrolytic cell that is too complex and which cannot be easily maintained.
Accordingly, there is a need for a wastewater treatment system and process that removes contaminants, such as petroleum hydrocarbons, resulting in a product with impurities of considerably less than 15 parts per million (PPM), that is cost effective, energy conscious, easy to use and easy to maintain.
The present invention is directed to a treatment for water and wastewater and a process for removal of contaminants by utilizing chemical, mechanical, and electrolytic devices.
It is an object of this invention to provide a treatment system and process of removal that removes impurities from water and wastewater.
It is also an object of this invention to provide a treatment system and process of removal of contaminants from wastewater that is cost effective and energy efficient.
It is a further object of this invention to provide a treatment system and process of removal of contaminants from water and wastewater that is easy to use and easy to maintain.
In general, the subject invention has potential application to treat water and wastewater rather than using chemical methods such as inorganic cationic coagulants including the salts of aluminum (aluminum sulfate or xe2x80x9calumxe2x80x9d, aluminum chloride, or poly aluminum chloride), iron (chlorides or sulfates), or calcium (chlorides or sulfates). In addition, sediments may be removed in the preparation of potable water. The subject invention may also be used as an aid to clarify water following biological treatment of wastewater.
A more complete understanding of the waste water treatment system and process for the removal of contaminants will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiments. Reference will be made to the appended sheets of drawings, which will first be described briefly.